It is known that thermoplastic tier sheets have been conventionally employed, for example, for supporting and restraining a multiplicity of empty cans, such as, for example, aluminum cans, wherein the multiplicity of empty aluminum cans are adapted to be disposed in tiered arrays upon a plurality of tier sheets such that the assembly or tiered arrays of tier sheets and empty aluminum cans can be disposed upon a transportation pallet so as to effectively form a palletized load which is being shipped, for example, from a can manufacturer to a vendor such that the empty cans can be filled with a product. In connection with the manufacture or fabrication of such tier sheets, it is desirable that the tier sheets exhibit predetermined degrees, properties, characteristics, or qualities of softness, flexibility, elasticity, and resiliency in order to in fact serve their useful or desired purposes or objectives. For example, each tier sheet must exhibit a predetermined amount or degree of softness such that the cans can, in effect, form impressions or depressions within the upper and lower tier sheets as the different tiers or layers of tier sheets and cans are disposed upon the transportation pallet within the aforenoted tiered array. As a result of the cans effectively defining impressions or depressions within the upper and lower tier sheets, movement of the individual cans with respect to the upper and lower tier sheets will effectively be restricted and prevented. In addition, the tier sheets need to be sufficiently flexible such that the edges of the tier sheets can bend without experiencing significant deformation during, for example, their disposition and packaging upon the transportation pallets when the palletized loads are being formed. Furthermore, the tier sheets must be sufficiently elastic and resilient whereby, after the cans are removed from the tier sheets, the structure comprising the tier sheets can dimensionally recover such that the depressions and impressions, previously formed within the tier sheets, will effectively disappear so as to thereby enable the tier sheets to be readied for use with respect to new or additional sets of cans in connection with the formation of subsequent palletized loads.
A first conventional, PRIOR ART type of tier sheet, currently being manufactured and marketed, is illustrated in FIG. 1 and is generally indicated by the reference character 10. It is seen that the tier sheet 10 comprises a three-layer laminate structure which comprises a pair of outer layers or members 12,14 which are fabricated from a suitable polypropylene homopolymer, and an inner core layer or member 16 which is fabricated from a suitable polypropylene copolymer. The laminate structure 10 comprises a three-layer extrusion and may have a thickness dimension of approximately 25 mils wherein each one of the outer layers or members 12,14 has a thickness dimension of approximately 1-2 mils. While the tier sheet 10 has proven to be substantially satisfactory, it is desirable that the tier sheet 10 in fact exhibit a greater degree of softness, flexibility, elasticity, and resiliency. As has been noted hereinbefore, it is desired that each tier sheet exhibit a predetermined amount or degree of softness such that the cans can, in effect, form sufficiently large or deep impressions or depressions within the upper and lower tier sheets as the different tiers or layers of tier sheets and cans are disposed upon the transportation pallet within the aforenoted tiered array comprising the palletized load. In this manner, movement of the individual cans with respect to the upper and lower tier sheets will effectively be restricted and prevented.
In addition, each one of the tier sheets 10 needs to be sufficiently flexible such that the edges of the tier sheets can bend without experiencing significant deformation during, for example, their disposition and packaging upon the transportation pallets when the palletized loads are being formed. Furthermore, each one of the tier sheets 100 must be sufficiently elastic and resilient whereby, after the cans are removed from the tier sheets, the laminate structure comprising each tier sheet 10 can dimensionally recover such that the depressions and impressions, previously formed within each tier sheet 10, will effectively disappear so as to thereby enable each tier sheet 10 to be readied for use with respect to supporting and restraining new or additional sets of cans in connection with the formation of subsequent palletized loads.
A second conventional, PRIOR ART type of tier sheet, being currently manufactured and marketed under the trademark TYPAR®, is disclosed within FIG. 2 and is generally indicated by the reference character 110. The second conventional, PRIOR ART tier sheet 110 is also seen to comprise a three-layer laminate structure which comprises a pair of outer layers or members 112,114 which are fabricated from a suitable polypropylene impact copolymer, and an inner core layer or member 116 which is fabricated from a suitable non-woven polypropylene homopolymer, the three layers or members 112,114,116 being bonded together either by means of a suitable heat-treatment process or by means of a suitable adhesive bonding material. While the second type of tier sheet 110 does exhibit improved softness, flexibility, elasticity, and resiliency properties or operational characteristics, relative to, for example the first type of tier sheet 10 as disclosed within FIG. 1, it is noted that the second type of tier sheet 110 does exhibit some operational or service life disadvantages or drawbacks.
For example, in view of the fact that the three layers or members 112,114,116 of the tier sheet 110 have been bonded together either by means of a suitable heat-treatment process or by means of a suitable adhesive bonding material, the tier sheet 110 can suffer delamination as disclosed within FIG. 3, wherein it is seen, for example, that the upper outer layer or member 112 has effectively become separated from the sub-assembly comprising the inner core layer or member 116 and the lower outer layer or member 114. Continuing still further, since the inner core layer or member 116 is fabricated from a suitable non-woven polypropylene homopolymer, and in view of the additional fact that the three layers or members 112,114,116 are simply bonded together by means of a suitable heat-treatment process, or by means of a suitable adhesive bonding material, wherein, for example, the exposed edge portions of the tier sheet laminate 110 are not sealed, then the tier sheet 110 will tend to absorb moisture whereby the structural integrity of the tier sheet 110 will, in turn, tend to rapidly deteriorate.
A need therefore exists in the art for a new and improved new and improved tier sheet which therefore not only exhibits extremely favorable and desirable degrees, properties, characteristics, or qualities of softness, flexibility, elasticity, and resiliency, but in addition, the new and improved tier sheet must also be free from the structural drawbacks, defects, or operational disadvantages comprising the absorption of moisture and the delamination of its plurality of layers.